Casting furnace and method for continuous casting of molten magnesium

Abstract

A casting furnace for continuous casting of magnesium comprises a furnace body divided into at least two compartments by at least one vertical weir. Inside each compartment, an upper layer of molten magnesium is in contact with a lower layer of a liquid heating medium, preferably a molten salt. The top of the weir is situated below a maximum level of the molten magnesium in the furnace. The weir is free of openings between its top and the magnesium/salt interface. The molten magnesium from primary (electrolytic) production or an alloy preparation furnace is introduced into a feed compartment of the furnace through a discharge pipe having means to direct the magnesium horizontally along the magnesium/salt interface, thereby minimizing intermixing of the magnesium and salt layer. The weir(s) separating the compartments minimize the effects of turbulence on the magnesium being pumped from the extraction compartment and also assist in minimizing the intermixing of the magnesium and salt layers, thereby providing a more energy efficient casting process capable of producing high quality castings.

What is claimed is:  
     
       1. A casting furnace for continuous casting of molten magnesium in which a layer of said molten magnesium is maintained in contact with a layer of a liquid heating medium having greater density than said molten magnesium, said casting furnace comprising: 
       a furnace body for containing said molten magnesium and said liquid heating medium, said furnace body having side walls and a bottom wall, with inner surfaces of said walls having a refractory lining;  
       at least one vertical weir extending between two of said side walls and dividing said furnace body into a plurality of compartments, said plurality of compartments including a feed compartment into which said molten magnesium is introduced and an extraction compartment from which said molten magnesium is removed for casting, said at least one vertical weir having a top which is situated below a maximum level of said molten magnesium and a bottom which is situated below an interface between the molten magnesium and the heating medium, with an opening being provided between the bottom of the at least one vertical weir and the bottom wall of the furnace body, said at least one vertical weir being free of openings between its top and the interface;  
       a charging pipe through which magnesium is introduced into said feed compartment, said charging pipe having a discharge end which is located below the top of the at least one vertical weir and above the interface between the molten magnesium and the heating medium;  
       magnesium redirection means provided at the discharge end of the charging pipe, said redirection means having a redirecting portion extending substantially parallel to the interface and spaced therefrom so as to direct said molten magnesium along the interface; and  
       heating means to maintain said liquid heating medium and said molten magnesium in a liquid state.  
     
     
       2. A casting furnace as claimed in  claim 1  comprising one said vertical weir, said weir separating said feed compartment from said extraction compartment. 
     
     
       3. A casting furnace as claimed in  claim 1 , wherein said redirecting portion of said magnesium redirection means is positioned horizontally and substantially parallel to the interface between the molten magnesium and the heating medium. 
     
     
       4. A casting furnace as claimed in  claim 1 , wherein said magnesium redirection means comprises a plate spaced from the discharge end of the charging pipe. 
     
     
       5. A casting furnace as claimed in  claim 4 , wherein said plate is positioned horizontally and substantially parallel to the interface between the molten magnesium and the heating medium. 
     
     
       6. A casting furnace as claimed in  claim 5 , wherein said plate has dimensions which are substantially the same as the diameter of the discharge end of the discharge pipe. 
     
     
       7. A casting furnace as claimed in  claim 6 , said magnesium redirection means additionally comprising a mounting bracket by which the plate is connected to the charging pipe. 
     
     
       8. A casting furnace as claimed in  claim 1 , wherein said furnace body has a top comprised of a refractory material, said top including removable covers to provide access to said plurality of compartments. 
     
     
       9. A casting furnace as claimed in  claim 1 , wherein said opening in the bottom of the vertical weir is arch-shaped. 
     
     
       10. A casting furnace as claimed in  claim 1 , wherein said at least one vertical weir is free of openings between its bottom and its top. 
     
     
       11. A casting furnace as claimed in  claim 1 , wherein said at least one vertical weir is substantially perpendicular to a furnace axis. 
     
     
       12. A casting furnace as claimed in  claim 1 , further comprising a partition wall located upstream of the at least one vertical weir, said partition wall having a top which is situated above the maximum level of said molten magnesium and a bottom which is situated below the interface between the molten magnesium and the heating medium, with an opening being provided between the bottom of the partition wall and the bottom wall of the furnace body, said partition wall being free of openings between its top and the interface, said partition wall forming a liquid heating medium compartment which is substantially free of said molten magnesium. 
     
     
       13. A casting furnace as claimed in  claim 1 , wherein said heating means comprises a set of electrodes which are in contact with said layer of liquid heating medium. 
     
     
       14. A method for continuous casting of molten magnesium, comprising: 
       charging said molten magnesium through a charging pipe into a feed compartment of a casting furnace in which a layer of said molten magnesium is maintained in contact with a layer of a liquid heating medium having greater density than said molten magnesium, said molten magnesium being introduced into said feed compartment above an interface between the molten magnesium and the liquid heating medium;  
       as the molten magnesium is introduced into the feed compartment, directing it parallel to the interface toward a vertical weir dividing said feed compartment from an extraction compartment of the casting furnace, said vertical weir having a top which is situated below a maximum level of said molten magnesium and a bottom which is situated below the interface between the molten magnesium and the heating medium;  
       withdrawing said molten magnesium from said extraction compartment.